Chrome-iron compound and method of making same.



UNITED STATES PATENT OFFICE.

ALEXANDER GEORGE MCKENNA, OF VVILKINSBURG, PENNSYLVANIA, ASSIGNOR, BY MESNE ASSIGNMENTS, TO THE FIRTH-STERLING STEEL COMPANY, OF PITTSBURG, PENNSYLVANIA.

CHROME-IRON COMPOUND AND METHOD OF MAKING SAME.

SPECIFICATION forming part of Letters Patent No. 637,013, dated November 14, 1899.

Application filed June 10, 1897. Serial No. 640,218. (Specimens) To all whom it may concern.-

Be it known that I, ALEXANDER GEORGE MCKENNA, a resident of Wilkinsburg, in the county of Allegheny and State of Pennsylvania,have invented anew and useful Improvement in Chrome-Iron Compounds and Methods of Making the Same; and I do hereby declare the following to be a full, clear, and exact description thereof.

My invention relates to the production of a material to be used in introducing chromium into steel without at the same time introducing an undesirable quantity of carbon. To obtain this result, the only practicable way heretofore known to me has been by the use of practically pure chromium of necessarily high cost.

The object of the present invention is to produce at a comparatively low cost a suitable material which will take the place of this pure chromium as an alloy or, as it is termed, a medicine added to the steel before or during melting and by which the high-chrome and low-carbon steel can be produced.

To these ends my invention consists in raising a mixture of pulverized ferrochromium containing carbon and pulverized green oxid of chromium to a high heat bufaheat below the melting-point of the mass, and thereby reducing the green oxid and partially burning off the carbon, producing an aggregated mass composed of iron and chromium practically free from or very low in carbon.

It also consists in the article produced.

In the practice of myinvention I prefer to employaternary alloy of iron, chromium, and carbon, which is free or practically free from sulfur, phosphorus, silicon, and manganese, and which is as high as practicable in proportion of chromium. Such alloy can be obtained by approved methods with a propor tion of from sixty to seventy per cent. of chromium, twenty to thirty per cent. of iron, and eight to ten per cent. of carbon, and it is preferred to employ such an alloy high in chromium as giving the best results. This alloy is of brittle nature and it is first pulverized, which is intended to include the crushing or grinding of the same to a condition of shot or powder, after which it is mingled with pulverized green oxid of chromium in approximately the right proportion to provide the necessary oxygen for the oxidation of the carbon in the alloy and to the reduction of the chromium of the green oxid to metallic form or to a lower oxid. It is preferred that the green oxid of chromium employed shall be free from sulfur. While the process is preferably practiced with the high grades of alloys above described, it has great advantages when used with alloys of lower grade and is of course intended to be used therewith.

I have found that practically the best re sults are obtained from mixing the alloy and oxid in the proportions of about eighty per cent. of the alloy and twenty per cent. of the chrome-oxid, and after the two are thoroughly commingled they are placed in a crucible which has previously been used in the making of steel, it being preferred to employ worn-out crucibles for the purpose because it is necessary to break the crucible to obtain the resultant product. The crucible is placed in the ordinary steel-melting furnace and is raised to the high steel-melting heat .and maintained at that heat for a considerable period, my experience being that four or five hours are sufficientfor the complete re duction or treatment. So far as learned, the resultant action is that the materials are only partially melted under the high heat, part only being brought to a molten state. The heat is sufficient to partially free the carbon from the alloy and the oxygen from the green oxid, which unite and burn, so reducing practically all the oxid to a metallic state or to a lower chrome-oxid or to such a state that it readily enters into the steel and burning off a large proportion of the carbon, it being observed that during the treatment the resultant gas burns with a blue flame at the mouth of the pot or crucible. When the pot is withdrawn from-the furnace, it is allowed to cool and is then broken to obtain the resultant product, which is an agglomerated mass having exposed metallic surfaces and having portions apparently covered with a thin coating of the chrome-oxid not entirely reduced.

molten under the treatment. It is found that the resultant product loses in weight under the treatment, due to the loss of the carbon in the alloy and the oxygen in the oxid, and it is further found that whatever carbon is present has no practical effect upon the resultant alloys into which the product enters.

As the chrome-iron alloy which is treated according to this process can be produced at much lower cost from the ordinary chrome ore than the cost of the green oxid free from sulfur, the resultant product is much lower in cost than the green oxid and gives practically as good results as the high-priced metallic chromium when alloying with steel or other metals with which it is desired to employ the same. Vhen the product is to be employed for forming steel-alloy, it is preferably crushed before being introduced into the steel and is introduced into the same either before or during melting.

What I claim as my invention, and desire to secure by Letters Patent, is

1. The process of forming a chrome-iron product or alloy, consisting in mixing an alloy of iron, chromium and carbon with green oxid of chromium and raising the mass to such a heat that part only is brought to a molten state, substantially as set forth.

2. A chrome-iron product consisting of an aggregated mass of an alloy of iron and chromium, and having exposed faces in part metallic and in part coated with oxid of chromium, substantially as set forth.

In testimony whereof I, the said ALEXAN- DER GEORGE MoKnNNA, have hereunto set my hand.

ALEXANDER GEORGE MGKENNA.

Witnesses:

ROBERT C. TOTTEN, WALTER FAMARISS. 

